Three identical-looking metal bars, labeled XXX, YYY, and ZZZ, are made of a ferromagnetic material. Two of these bars are permanently magnetised, and one is unmagnetised.
Describe and explain how a student can identify which bar is unmagnetised, using only the three bars and without any other apparatus.
A step-down transformer is connected to a 230 V230\text{ V}230 V AC mains supply. The output power from the transformer is 46 W46\text{ W}46 W and the transformer is 100%100\%100% efficient.
Calculate the input current to the primary coil of the transformer.
State a suitable material for the transformer core and a suitable material for the coils.
275 exam-style questions on CIE IGCSE Physics 4.5 Electromagnetic effects, covering 4.5.1a Electromagnetic induction, 4.5.1b Direction of an induced e.m.f., 4.5.2 The a.c. generator, 4.5.3a Magnetic effect of a current and its applications, 4.5.3b Strength and direction of the field around wires and solenoids, 4.5.4a Force on a current-carrying conductor, 4.5.4b Force on beams of charged particles, 4.5.5 The d.c. motor, 4.5.6a Construction and operation of a transformer, 4.5.6b Turns ratio and current in a transformer, and 4.5.6c High-voltage transmission of electricity. Each one has a worked solution and a mark scheme showing where the marks go.